This project is concerned with the normal physiology of the ear and the pathological conditions that result in deafness. The basic purpose of this program project is to provide for the core support of the Kresge Hearing Research Institute so that individual investigators can pursue specific research projects without concern for the financial support of administrative or technical personnel that are necessary for all projects. It is of course, the research itself that proves the worth of the core support but, for the most part, the specific demands for directly applicable equipment, supplies and laboratory assistants are individually supported within the Institutes core support framework. Many laboratories utilizing different techniques are involved in this study of the causes of deafness. Microcirculation of the ear in normal conditions and under the influence of ototoxic drugs, noise and congenital abnormalities are studied by closed circuit television in relation to the energy transformation ability of the ear. Monkeys are trained so that thresholds and recruitment determinations can be made on them. These animals are used in studies of the pathology of ototoxicity, temporary and permanent threshold shifts. The chemical alteration of fluids and cells is analyzed and the architectural pathology is determined by histological surface preparation, transmission and scanning electron microscopy. The psychoacoustic anomalies of the function of the neural pathways is studied by microelectrode.